In trying to build Complexity I ran into some build errors. First, you need to update your pull of gnulib because yours still refers to gets, which was removed from libc, resulting in this error:

In file included from freading.h:18:0,
from freading.c:20:
./stdio.h:1048:1: error: 'gets' undeclared here (not in a function)

Once references to gets are removed from stdio.in.h, I run into errors in building ftello.c from gnulib, which is strange because the system I am building on should not neet gnulib's version:

ftello.c: In function 'rpl_ftello':
ftello.c:45:7: error: 'fp_' undeclared (first use in this function)
ftello.c:45:7: note: each undeclared identifier is reported only once for each function it appe
ars in
ftello.c:45:20: error: '_IOWRT' undeclared (first use in this function)

I can find very few references to similar build errors but I have found a couple in gnutls from a year or so ago. It seems there's some problem in the configure script not properly handling the ftello checks. If I remove this check, then the build proceeds as normal.

Finally, I run into problems with your bool_t enum in complexity.h:

In file included from opts.h:210:0,
from complexity.c:24:
complexity.h:42:16: error: expected identifier before numeric constant

It would appear that "true" and "false" are declared as constants elsewhere but I could not find the definition in a cursory search. Simply renaming the enum members to TRUE and FALSE sufficed to fix the problem, so my suspicion is probably correct.

Once I correct all of these the build works fine. I hope this information helps!